Stimuli-responsive hybrid microgels for controlled drug delivery: Sorafenib as a model drug

Microgels (MGs) are synthetic colloidal hydrogel particles made of three dimensional polymer networks. Their chemical composition is crucial for their use as intelligent drug release systems operated by temperature control. Herein, several MGs using N-isopropylacrylamide (Nipam)/N-isopropylmethacrylamide (Nipmam), chitosan and acrylic/methacrylic acid have been synthesized by free radical polymerization reactions (NC MGs) and the effects of surfactants and different reaction times on size and swelling properties have been investigated. MGs have been identified and characterized by dynamic light scattering and atomic force microscopy, and finally used to optimize the encapsulation protocol of the hydrophobic drug sorafenib. The drug delivery system here described has encapsulation efficiency of 40% and releases 10% of the entrapped drug over about 16 h after the temperature is raised above the volume phase transition temperature. Data suggest that MGs with optimized composition may act as properly instructed entities able to trap and release biomolecules following external stimuli.